Duplicating Plasmonic Hotspots by Matched Nanoantenna Pairs for Remote Nanogap Enhanced Spectroscopy
Yang Li, Huatian Hu, Wei Jiang, Junjun Shi, Naomi J. Halas, Peter Nordlander, Shunping Zhang, Hongxing Xu
Abstract
Plasmonic nanoantennas are capable of reversibly interconverting free-space radiation with localized modes at the nanoscale. However, optical access to a single nanoantenna, through a laser beam, is always accompanied by disruptive background perturbations and heating effects. Remote spectroscopy is one promising route to overcome these effects. Here, we demonstrate excitation-collection-separated enhanced spectroscopy using a matched nanoantenna pair. The receiving and transmitting antennas are geometrically separated but bridged by the propagating surface plasmon polaritons (SPPs) on the metal film. The receiving antenna, consisting of a silver nanowire on a mirror, ensures a high light-to-plasmon conversion efficiency. The transmitting antenna consists of a silver nanocube over a mirror and is impedance matched to free space photons and the propagating SPPs. As a proof-of-principle, we demonstrate remote surface-enhanced Raman scattering with a high signal-to-noise ratio. This matched nanoantenna pair may have applications for remote entanglement of quantum emitters, biochemistry detection, or optical interconnects.